Going to the beach makes Cassie go low. It's only natural: the exercise playing in the surf, the stress the sun puts on her little body and just the sheer excitement of being on the shore. So naturally we keep the pump off most of the time and keep lots of snacks and drinks handy.
One tip: before we take the pump off, we give her a little bolus to replace some of the basal insulin that she'll be missing.
Another tip: Insulin is VERY sensitive to heat. We bring a soft cooler with an adjacent "dry" compartment and keep it in the shade. We keep her pump in it and it helps protect the insuling from "cooking" in the sun.